Here's Why Spider-Man Would Need Size 100 Feet to Scale Walls

Spider-Man's power to scale walls is inspired by the animal kingdom—spiders, of course, but also other species of insects, reptiles, amphibians, and small mammals have this ability. But could a human ever do it in real life, using sticky adhesives like these animals? Not according to a recent study from University of Cambridge, which claims that anatomical constraints would prevent a human from ever climbing a wall Peter Parker-style, unless someone were born with size 100 feet.

According to the study, the largest animal that could possibly manage to scale a wall is approximately the size of a gecko. Geckos can climb vertical surfaces as a result of billions of sticky hairlike structures on the bottoms of their feet, similar to other wall-climbing species like spiders, cockroaches, beetles, bats, tree frogs, and lizards. But just as proportional strength decreases as body mass increases (see: Ant-Man, or actual ants), it becomes more and more difficult to support a body with adhesives as body surface area grows larger.

As a result, the percentage of surface area that needs to be covered in adhesive is directly proportional to size; so while geckos can climb walls using only their feet, Spider-Man would need to be covered in adhesives on 40% of his body, and 80% of his front.

"As animals increase in size, the amount of body surface area per volume decreases — an ant has a lot of surface area and very little volume, and an elephant is mostly volume with not much surface area," said author David Labonte in a press release (via Wired). "This poses a problem for larger climbing animals because, when they are bigger and heavier, they need more sticking power, but they have comparatively less body surface available for sticky footpads. This implies that there is a maximum size for animals climbing with sticky footpads – and that turns out to be about the size of a gecko."

So if we wanted to climb a wall using only our feet, as Spider-Man does, it would take a whole lot of surface area that probably isn't anatomically feasible (or the help of a radioactive spider and comic book scientific laws).

"If a human wanted to climb up a wall the way a gecko does, we'd need impractically large sticky feet-and shoes in European size 145 or US size 114," said co-author Walter Federle.